1. Field of the invention
The present invention relates generally to a method of controlling the dimensional and surface characteristics of portions of a mandrel wound composite shaft, and specifically to a method of modifying the fabricating technique of a composite shaft which has at least one flared end, and a tool used in the modified fabrication technique.
The composite shafts are fabricated from continuous filaments in either a roving or tape form within a resin matrix and subsequently cured to form a rigid monolithic structure. The composite shafts fabricated may be used in a static structural application or in a dynamic environment where they may be required to transmit torque and power.
2. Prior Art
Composite shafts and apparatus for fabricating them are known. See, for example, U.S. Pat. No. 3,733,233. In this patent, filament winding is disclosed as the preferred mode of fabrication. Instead of the filament winding, however, a tape winding could be used. To couple the shafts fabricated in accordance with the teaching of the noted patent, the shaft ends must be modified or a coupling provided. An example of such an end modification can be seen in U.S. Pat. No. 4,362,521. In this patent a metal end fitting is provided which is pushed into the shaft end and is engaged by a pair of bolts for torque transmission. The shaft end which accommodates the metal end fitting is provided with a cemented-in sleeve and a cemented-on tubular portion so that the wall thickness of the shaft is not uniform along its length. According to another known end modification technique, an end fitting is wound into the shaft end and as such is locked-in and cannot be removed. Since such designs generally require a thicker wall in the coupler/ fastener area their is an associated penalty of cost and weight because extra meterial is required. Also, pin or bolt holes in a composite structure are undesirable because they cut the load carrying filaments and introduce an interlaminar shear condition, i.e., one requiring the resin to transfer load to the next fiber. These coupler/fastener designs are undesirable from a structural standpoint. They are also undesirable because they compromise the simplicity of mandrel winding due to the need to alter the winding schedule in order to properly secure the coupler/fastener, or build-up material in the coupler portion of the shaft.
It would be desirable, therefore, to fabricate a composite shaft which has a generally uniform wall thickness along its length, which does not require a permanently secured coupler/fastener, which does not require that its ends have holes formed therein, and which does not compromise the simplicity of, for example, a filament winding techinque. Also, it would be desirable to fabricate a composite shaft which does not require any substantial amount of machining and eliminates inner and outer machining at its ends.